1. Field of Invention
The present invention relates to a composite thin-film magnetic head comprising a recording head and a reproducing head and a method of manufacturing such a thin-film magnetic head, and to a thin-film magnetic head sub-structure used for producing such a thin-film magnetic head and a method of manufacturing such a thin-film magnetic head sub-structure.
2. Description of Related Art
Performance improvements in thin-film magnetic heads have been sought as surface recording density of hard disk drives has increased. Composite thin-film magnetic heads have been widely used. A composite head is made of a layered structure including a recording head having an induction magnetic transducer for writing and a reproducing head having a magnetoresistive (MR) element for reading. MR elements include an an isotropic magnetoresistive (AMR) element that utilizes the AMR effect and a giant magnetoresistive (GMR) element that utilizes the GMR effect. A reproducing head using an AMR element is called an AMR head or simply an MR head. A reproducing head using a GMR element is called a GMR head. An AMR head is used as a reproducing head whose surface recording density is more than 1 gigabit per square inch. A GMR head is used as a reproducing head whose surface recording density is more than 3 gigabits per square inch.
An AMR head comprises an AMR film having the AMR effect. In place of the AMR film a GMR head comprises a GMR film having the GMR effect. The configuration of the GMR head is similar to that of the AMR head. However, the GMR film exhibits a greater change in resistance under a specific external magnetic field compared to the AMR film. As a result, the reproducing output of the GMR head is about three to five times as great as that of the AMR head.
The MR film may be replaced in order to improve the performance of a reproducing head. In general, an AMR film is made of a magnetic substance that exhibits the MR effect and has a single-layer structure. In contrast, many of GMR films have a multilayer structure consisting of a plurality of films. There are several types of mechanisms of producing the GMR effect. The layer structure of a GMR film depends on the type of mechanism. GMR films include a superlattice GMR film, a granular film, a spin valve film and so on. The spin valve film is most efficient since the film has a relatively simple structure, exhibits a great change in resistance in a low magnetic field, and suitable for mass production. The performance of the reproducing head is thus easily improved by replacing the AMR film with a GMR film and the like with an excellent magnetoresistive sensitivity.
Besides selection of a structure as described above, a pattern width such as an MR height, in particular, determines the performance of a reproducing head. The MR height is the length (height) between the end of the MR element closer to the air bearing surface (medium facing surface) and the other end. The MR height is basically controlled by an amount of lapping when the air bearing surface is processed.
Performance improvements in a recording head are also required as the performance of a reproducing head is improved. It is required to increase the track density on a magnetic recording medium in order to increase recording density among the performance characteristics of a recording head. To achieve this, it is required to implement a recording head of a narrow track structure by performing submicron processing on a magnetic layer making up a top pole through the use of semiconductor process techniques. It is also required to use a magnetic material having higher saturation flux density.
Another factor determining the recording head performance is a throat height. The throat height is the length (height) of a portion (called a pole portion in the invention) between the air bearing surface and the end of the insulating layer electrically isolating the thin-film coil. A reduction in throat height is desired in order to improve the recording head performance. The throat height is controlled as well by an amount of lapping when the air bearing surface is processed.
As thus described, it is important to fabricate well-balanced recording and reproducing heads to improve the performance of a thin-film magnetic head.
Reference is now made to FIG. 15A to FIG. 23A, FIG. 15B to FIG. 23B, and FIG. 24 to FIG. 27 to describe an example of a manufacturing method of a composite thin-film magnetic head as an example of a manufacturing method of a related-art thin-film magnetic head. FIG. 15A to FIG. 23A are cross sections each orthogonal to the air bearing surface. FIG. 15B to FIG. 23B are cross sections each parallel to the air bearing surface of the pole portion.
According to the manufacturing method, as shown in FIG. 15A and FIG. 15B, an insulating layer 102 made of alumina (Al2O3), for example, of about 5 to 10 xcexcm in thickness is deposited on a substrate 101 made of aluminum oxide and titanium carbide (Al2O3xe2x80x94TiC), for example.
Next, as shown in FIG. 16A and FIG. 16B, on the insulating layer 102 a bottom shield layer 103 made of a magnetic material is formed for a reproducing head.
Next, as shown in FIG. 17A and FIG. 17B, on the bottom shield layer 103 alumina or aluminum nitride, for example, of 100 to 200 nm in thickness is deposited through sputtering to form a bottom shield gap film 104 as an insulating layer. On the bottom shield gap film 104 an MR film of tens of nanometers in thickness is formed for making an MR element 105 for reproduction. Next, with a photoresist pattern as a mask, the MR film is etched through ion milling, for example, to form the MR element 105. The MR element 105 may be either a GMR element or an AMR element.
Next, as shown in FIG. 18A and FIG. 18B, a top shield gap film 106 is formed as an insulating layer on the bottom shield gap film 104 and the MR element 105. The MR element 105 is embedded in the shield gap films 104 and 106.
Next, as shown in FIG. 19A and FIG. 19B, on the top shield gap film 106 a top shield layer-cum-bottom pole layer (called top shield layer in the following description) 107 is formed. The top shield layer 107 is made of a magnetic material and used for both a reproducing head and a recording head.
Next, a recording gap layer 108 made of an insulating film such as an alumina film is formed on the top shield layer 107. Next, the recording gap layer 108 is partially etched in a backward portion (the right side of FIG. 19A) to form a contact hole for making a magnetic path. Next, a top pole tip 109 for the recording head is formed on the pole portion of the recording gap layer 108. The top pole layer 109 is made of a magnetic material such as Permalloy (NiFe) or FeN as a high saturation flux density material. At the same time, a magnetic layer 119 made of a magnetic material is formed for making the magnetic path in the contact hole for making the magnetic path.
Next, the recording gap layer 108 and the top shield layer (bottom pole layer) 107 are etched through ion milling, using the top pole tip 109 as a mask. As shown in FIG. 19B, the structure is called a trim structure wherein the sidewalls of the top pole (the top pole tip 109), the recording gap layer 108, and part of the top shield layer (bottom pole layer) 107 are formed vertically in a self-aligned manner. The trim structure suppresses an increase in the effective track width due to expansion of the magnetic flux generated during writing in a narrow track.
Next, as shown in FIG. 20A and FIG. 20B, an insulating layer 110 of alumina, for example, having a thickness of about 3 xcexcm is formed over the entire surface. The insulating layer 110 is polished to the surfaces of the pole tip 109 and the magnetic layer 119 and flattened. The polishing method may be mechanical polishing or chemical mechanical polishing (CMP). The surfaces of the pole tip 109 and the magnetic layer 119 are thereby exposed.
On the flattened insulating layer 110 a photoresist layer 111 is formed into a specific pattern through high-precision photolithography. Next, on the photoresist layer 111 a thin-film coil 112 of a first layer is made for the induction-type recording head. The thin-film coil 112 is made of copper (Cu), for example.
Next, as shown in FIG. 21A and FIG. 21B, a photoresist layer 113 is formed into a specific pattern on the photoresist layer 111 and the coil 112. Heat treatment is performed at a temperature of 250 to 300xc2x0 C., for example, to flatten the surface of the photoresist layer 113.
Next, as shown in FIG. 22A and FIG. 22B, a thin-film coil 114 of a second layer is formed on the photoresist layer 113. Next, a photoresist layer 115 is formed into a specific pattern on the photoresist layer 113 and the coil 114. Heat treatment is performed at a temperature of 250 to 300xc2x0 C., for example, to flatten the surface of the photoresist layer 115.
Next, as shown in FIG. 23A and FIG. 23B, a top yoke layer 116 for the recording head is formed on the top pole tip 109, the photoresist layers 111, 113 and 115 and the magnetic layer 119. The top yoke layer 116 is made of a magnetic material such as Permalloy. Next, an overcoat layer 117 of alumina, for example, is formed to cover the top yoke layer 116. Finaymachine processing of the slider is performed to form the air bearing surface of the recording head and the reproducing head. The thin-film magnetic head is thus completed.
FIG. 24 and FIG. 25 show the completed thin-film magnetic head. FIG. 24 is a cross section of the head orthogonal to the air bearing surface 120. FIG. 25 is an enlarged cross section of the pole portion parallel to the air bearing surface 120. In FIG. 24 the throat height is indicated with xe2x80x98THxe2x80x99 and the MR height is indicated with xe2x80x98MR-Hxe2x80x99. As shown in FIG. 25, a first conductive layer 121 is provided on the side of the MR element 105.
In addition to the throat height and the MR height, another factor that determines the performance of a thin-film magnetic head is an apex angle as indicated with xcex8 in FIG. 24. The apex is a hill-like coil portion covered with the photoresist layers 111, 113 and 115. The apex angle is an angle formed between the top surface of the insulating layer 110 and the straight line drawn through the edges of the pole-side lateral walls of the apex.
FIG. 26 is a top view of the thin-film magnetic head manufactured as described above in a state halfway through the manufacturing process. FIG. 27 is a top view of the head manufactured as described above. FIG. 26 shows the state wherein the bottom shield layer 103, the MR element 105, and the top shield layer (bottom pole layer) 107 are formed. The overcoat layer 117 is omitted in FIG. 27. FIG. 15A to FIG. 23A are cross sections taken along line 23Axe2x80x9423A of FIG. 27. FIG. 15B to FIG. 23B are cross sections taken along line 23Bxe2x80x9423B of FIG. 27.
The performance and characteristics of a thin-film magnetic head are mainly determined by the MR element of the reproducing head and the pole portion of the recording head. To be specific, the performance and characteristics of the reproducing head are mainly determined by the track width of the reproducing head, corresponding to the MR element width. The performance and characteristics of the recording head are mainly determined by the pole portion dimensions such as the throat height and the track width of the recording head. Therefore, the demands of clients of thin-film heads are concentrated on matters relating to the process of making the MR element of the reproducing head and the pole portion of the recording head, such as the track width of the reproducing head and the throat height and the track width of the recording head.
Therefore, in order to mass-produce thin-film magnetic heads that satisfy the specifications required by the customer, it is necessary that the manufacturing steps taken to fabricate the MR element and steps that follow should conform to the customer""s demands.
However, as described above with reference to the drawings, the steps taken to fabricate the MR element belong to the early part of the entire steps of mass-producing thin-film heads, according to the related-art method. This is similar to other prior-art methods of manufacturing thin-film heads. Therefore, the time required for steps taken to fabricate the MR element and steps that follow make up a great proportion of the time required for the entire steps in the prior-art methods. In the prior art a long cycle time is therefore required. The cycle time is a period required between receipt of an order from the customer and completion and shipment of products conforming to the specifications required by the customer. The cycle time is about 20 to 25 days, for example. It is 30 to 40 days in some cases. Even though an agreement is made in an early stage between the customer and the manufacturer with regard to the specifications of thin-film heads such as performance characteristics, it takes many days to finally ship products.
These days technology advances at a remarkable rate and improvements are noticeable in surface recording density and reproduction rate required by the customer. Accordingly, modifications and improvements are made to the specifications of hard disk drives of computers every several months. Therefore, the customer demands that thin-film heads meeting the requirements are shipped in a short time after the order. The manufacturer is thus required to design products meeting the specifications required by the customer, mass-produce and ship the products in a short time.
Under such circumstances, it is difficult to satisfy the customer""s requests since a long cycle time is required in prior art.
Inspections are performed on complete thin-film heads after the entire manufacturing steps are finished in prior art. As a result, even if nonconforming heads are produced during the manufacturing steps, it is impossible to eliminate them. It is therefore difficult to improve yields of complete products.
It is an object of the invention to provide a thin-film magnetic head and a method of manufacturing the same and a thin-film magnetic head sub-structure and a method of manufacturing the same for providing thin-film magnetic heads that meet the specifications required by the customer in a short time and for improving yields of thin-film magnetic heads.
A thin-film magnetic head of the invention comprises: a reproducing head including: a magnetoresistive element; a first shield layer and a second shield layer for shielding the magnetoresistive element, portions of the first shield layer and the second shield layer that face a recording medium being opposed to each other with the magnetoresistive element in between; a first insulating layer provided between the magnetoresistive element and the first shield layer and a second insulating layer provided between the magnetoresistive element and the second shield layer; and a recording head including: a first magnetic layer and a second magnetic layer magnetically coupled to each other and each made up of at least one layer and including magnetic pole portions opposed to each other and placed in regions on a side of ends of the magnetic layers facing toward a recording medium; a gap layer placed between the pole portions of the first and second magnetic layers; and a thin-film coil at least part of which is placed between the first and second magnetic layers and insulated from the first and second magnetic layers. The second shield layer includes a first portion placed in a plane the same as a plane in which the first shield layer is placed, the first portion being insulated from the first shield layer, and a second portion connected to the first portion and opposed to the first shield layer with the magnetoresistive element in between. The second shield layer also functions as the first magnetic layer. The at least part of the thin-film coil is placed between the first portion of the""second shield layer and the second magnetic layer.
According to the thin-film magnetic head of the invention, a thin-film magnetic head sub-structure comprising the first shield layer, the first portion of the second shield layer, and at least part of the thin-film coil may be manufactured. In response to the customer""s requests, the second portion of the second shield layer, the magnetoresistive element, and the second magnetic layer may be formed on the sub-structure.
The thin-film magnetic head may further comprise a conductive layer connected to the magnetoresistive element. The at least part of the conductive layer is placed between the first shield layer and the first portion of the second shield layer, being insulated from the first shield layer and the first portion. In this case the head may further comprise a shield layer for shielding the at least part of the conductive layer.
A method of manufacturing a thin-film magnetic head, and a thin-film magnetic head sub-structure and a method of manufacturing the same of the invention are used for manufacturing a thin-film magnetic head comprising a reproducing head and a recording head. In the head the reproducing head includes: a magnetoresistive element; a first shield layer and a second shield layer for shielding the magnetoresistive element, portions of the first shield layer and the second shield layer that face a recording medium being opposed to each other with the magnetoresistive element in between; a first insulating layer provided between the magnetoresistive element and the first shield layer and a second insulating layer provided between the magnetoresistive element and the second shield layer. The recording head includes: a first magnetic layer and a second magnetic layer magnetically coupled to each other and each made up of at least one layer and including magnetic pole portions opposed to each other and placed in regions on a side of ends of the magnetic layers facing toward a recording medium; a gap layer placed between the pole portions of the first and second magnetic layers; and a thin-film coil at least part of which is placed between the first and second magnetic layers and insulated from the first and second magnetic layers. In the head the second shield layer includes a first portion placed in a plane the same as a plane in which the first shield layer is placed, the first portion being insulated from the first shield layer, and a second portion connected to the first portion and opposed to the first shield layer with the magnetoresistive element in between. The second shield layer also functions as the first magnetic layer.
The method of manufacturing a thin-film magnetic head of the invention includes the steps of: forming the first shield layer and the first portion of the second shield layer to be placed in one plane and insulated from each other; forming at least part of the thin-film coil on the first portion of the second shield layer such that the coil is insulated from the first portion; forming the first insulating layer on the first shield layer; forming the magnetoresistive element on the first insulating layer; forming the second insulating layer on the magnetoresistive element; forming the second portion of the second shield layer on the second insulating layer; forming the gap layer on the second portion; and forming the second magnetic layer on the gap layer.
According to the method, a thin-film magnetic head sub-structure comprising the first shield layer, the first portion of the second shield layer, and at least part of the thin-film coil may be manufactured. In response to the customer""s requests, the second portion of the second shield layer, the magnetoresistive element, and the second magnetic layer may be formed on the sub-structure.
The method may further include the step of forming at least part of a conductive layer to be connected to the magnetoresistive element such that the at least part of the conductive layer is placed between the first shield layer and the first portion of the second shield layer, being insulated from the first shield layer and the first portion. In this case the method may further include the step of forming a shield layer for shielding the at least part of the conductive layer. A shield layer for shielding the at least part of the conductive layer may be formed at the same time in the step of forming the second magnetic layer. The at least part of the conductive layer and the at least part of the thin-film coil may be formed in one step. The at least part of the conductive layer may be formed by plating.
In the method the first shield layer and the first portion of the second shield layer may be formed by plating.
The thin-film magnetic head sub-structure comprises: the first shield layer; the first portion of the second shield layer placed in the same plane as the first shield layer, being insulated from the first shield layer; and at least part of the thin-film coil placed on the first portion of the second shield layer, being insulated from the first portion.
According to the thin-film magnetic head sub-structure of the invention, in response to the customer""s requests, the second portion of the second shield layer, the magnetoresistive element, and the second magnetic layer may be formed on the sub-structure to manufacture a thin-film magnetic head.
The thin-film magnetic head sub-structure may further comprise at least part of a conductive layer to be connected to the magnetoresistive element. The at least part of the conductive layer is placed between the first shield layer and the first portion of the second shield layer, being insulated from the first shield layer and the first portion.
The method of manufacturing a thin-film magnetic head sub-structure includes the steps of: forming the first shield layer and the first portion of the second shield layer to be placed in one plane and insulated from each other; and forming at least part of the thin-film coil on the first portion of the second shield layer such that the coil is insulated from the first portion.
According to the method of manufacturing a thin-film magnetic head sub-structure of the invention, the thin-film magnetic head material comprising the first shield layer, the first portion of the second shield layer, and at least part of the thin-film coil may be manufactured. In response to the customer""s requests, the second portion of the second shield layer, the magnetoresistive element, and the second magnetic layer may be formed on the sub-structure to manufacture a thin-film magnetic head.
The method may further include the step of forming at least part of a conductive layer to be connected to the magnetoresistive element such that the at least part of the conductive layer is placed between the first shield layer and the first portion of the second shield layer, being insulated from the first shield layer and the first portion. In this case the at least part of the conductive layer and the at least part of the thin-film coil may be formed in one step. The at least part of the conductive layer may be formed by plating.
In the method the first shield layer and the first portion of the second shield layer may be formed by plating.
Other and further objects, features and advantages of the invention will appear more fully from the following description.